This invention relates to improvements in jacking mechanisms, and more particularly, to jacking mechanisms for an offshore platform to effect relative vertical movement of the platform with respect to supporting legs carried thereby.
Offshore platforms are generally employed for supporting oil-drilling equipment or servicing equipment in the open sea. It is desirable that the platform be elevated above the water surface so as to be relieved of the effects of wave action. Customarily, the platform is mounted on a plurality of supporting legs which are lowered to the waterbed, and the platform is raised thereon to an elevated position above the water surface for effecting the necessary offshore operations.
Jacking mechanism is deployed on the platform for effecting relative vertical movement between the platform and the legs. While numerous forms of jacking mechanisms have been proposed heretofore (e.g., see U.S. Pat. Nos. 2,947,148 and 2,992,812), a highly efficient assembly has been disclosed in my U.S. Pat. No. 3,804,369 issued Apr. 16, 1974. In that patent, there is set forth a jacking mechanism including a pair of fluid-actuated, extendable and retractable jacking cylinders which can be coupled and uncoupled individually relative to the associated leg. The cylinders are double-acting and are operated 180.degree. out-of-phase such that one cylinder is being extended while the other is being retracted. A flexible line arrangement operatively connects the two cylinders such that the power output of one cylinder can be transmitted effectively to assist the other cylinder. Thus, both of the cylinders act in unison even though moving out-of-phase. Such alternating, synchronized operation utilizes maximum power and affords continuous jacking action without the pauses required to extend the jacks for alternate strokes which had been required previously.
Notwithstanding the highly unique features and significant advantages of my afore-described patented system, there remains room for improvement, especially in connection with installation of jacking mechanisms aboard the platform, isolation of the platform from shocks and other abrupt forces, and an efficient distribution of forces that are generated during jacking.
It is, therefore, an object of the present invention to improve the jacking mechanism to provide for easy installation on a platform.
It is another object of the invention to provide for isolating the jacking mechanism from serious shocks and other abrupt force applications.
It is a further object of the invention to provide for effectively distributing the jacking forces to minimize the stress being applied to the jacking mechanism support structure.
It is yet another object of the invention to reduce the cost of jacking systems and in which forces are effectively transferred between a pair of step-by-step jacking assemblies.